Mitigating the effects of heat waves on dairy production

Tuesday, August 5, 2014

Sustained heat waves can affect herd health, reduce milk levels and cause additional deaths. One answer is better ventilation, but researchers also suggest that better mapping of heat distribution in rural areas, advance warnings and preventive measures could also help

by MATT McINTOSH

The fact that hot temperatures cause significant stress in dairy cattle is well known, but the increasing threat posed by summer heat waves – defined by Environment Canada as three or more days with temperatures at or above 32 C – has caused some producers to look for more effective methods of protecting their herds, and their herds' milk production.

Two University of Guelph researchers, though, suggest that better mapping of heat distribution in rural areas, along with other heat-mitigation techniques, would significantly help producers maintain their herd health and milk production levels.

"Years ago, during really hot periods, we would sometimes see a 10 per cent drop in production," says Dave Johnston, owner of Mapleview Holsteins, a 66-cow, tiestall dairy operation located near Listowel. "A couple of days of really high temperatures were okay, but it was the third, fourth and fifth consecutive day when we really started noticing a drop."

In an effort to keep his cows from suffering heat-related stress, and consequently producing less milk, Johnston outfitted his dairy barn – a hybrid bank barn featuring a more modern addition – with a tunnel ventilation system. Using five 48-inch (approximately 122-centimetre) fans, Johnston's cooling system pulls air in from outside and forces it through the barn. Now, despite the fact that the air being pushed through the barn is often warm, Johnston says he seldom sees production drop more than two or three per cent. "It has a bonus of keeping the flies down too," he says.

Johnston's case, however, was not a unique one, and represents a problem experienced by many farmers in Ontario and across North America. An article entitled "Economic losses from heat stress by U.S. livestock industries," published in the Journal of Dairy Science in 2003, pegged the economic losses due to heat stress in the U.S. livestock sector at approximately $1.7 billion.

After analyzing data from a number of Canadian and foreign studies – including information provided by Dairy Farmers of Ontario – Olaf Berke, an associate professor with the Ontario Veterinary College's population medicine department at the University of Guelph, and Katherine Bishop, a masters student in population medicine, looked at the number of dairy cow deaths in Ontario during both heat waves and cooler control periods.

"Cows die every day, on some days more, on other days less," says Berke. "During the three-day heat waves, we observed an additional 26 deaths as compared to the control periods before and after the heat waves."

Berke says that, while another 26 dead cows spread over several heat waves may not seem like a significant amount, it is a number indicative of other, more pervasive heat-related problems. Death is the most extreme consequence intense heat can have on dairy cows, meaning "there is likely a significant amount" of milk production being lost, as well as other sickness and reduced fertility rates that have not yet been measured.

Unfortunately, preventing heat stress can be expensive in terms of equipment and electricity. After consulting with a private company to make sure his barn would be able to accommodate a tunnel ventilation system, Johnston explains that his "very effective" renovation cost about $15,000 to install. With five fans running continuously during very hot periods, says Johnston, his electricity costs can spike significantly.

According to Tom Sangster, ventilation specialist at Exeter's Exacon Inc., a manufacturing company specializing in ventilation, feeding and flooring products, the energy cost of running a single 1.5- or one-horsepower fan similar to those employed on Johnston's operation can range from $3 to $4 over a 24-hour period. For Johnston, that means his five fans can cost him an additional $20 every day.

"Sometimes the fans have to run continuously for several weeks or more and that can put your hydro bill up by $600," he says. "We make it back in keeping our production levels up, but you do notice bills like that."  

Despite the positive effect proper ventilation can have on milk production and fertility, says Sangster, the potentially high cost of running cooling systems is always a big concern for farmers. Such costs are also one of the reasons Berke and Bishop say some dairy producers might benefit from an early warning system that, unlike generic weather forecasting, focuses specifically on heat waves in rural areas, as well as the potential temperatures inside barns themselves.

"Certain things need preparation time and cannot be done right away, thus we need lead-time for preventive methods to be put in place," says Berke. "Some might need more time than others."

More specifically, Berke and Bishop say that producing maps visualizing the distribution of heat stress in the province's different regions can help producers identify if their herd is at a higher risk, and act to minimize the effect of heat waves in advance. Farmers without access to resources such as tunnel ventilation, for instance, could at least make sure their barns are ventilated as much as possible, that there is lots of water available, and that they check on the herd more often in case an emergency arises.

Ideally, says Berke, any rural-centred early warning system could eventually be incorporated in standard weather broadcasts.

Both Bishop and Berke say mapping heat distribution for rural areas would also allow local public health units in Ontario to implement cooling strategies and provide more specific media alerts in advance. This, they say, would help prevent an average of 300 additional emergency room visits at rural hospitals every time the province is hit with a heat wave.

"Heat waves and the heat stress they cause are a real problem," says Bishop. "They are likely having a major economic impact on dairy farmers in Ontario, and it's a problem that should be addressed." BF